I. Field of the Invention
The present invention relates to a back pressure inducer for use in a fluid system.
II. Description of the Prior Art
Back pressure inducers are commonly used in fluid systems in order to impose a resistance, i.e., create a pressure drop, to the fluid flow from one passageway or conduit to another. Such back pressure inducers are used in a plurality of different applications in fluid systems.
These previously known back pressure inducers typically comprise a flat plate having a circular hole and positioned in between the conduits so that the hole forms a fluid port between the conduits. A poppet valve member having an outwardly flared or conical valve head and an elongated stem extending axially away from the valve head is then positioned within the outlet conduit and so that the valve head registers with the fluid port. A spring retainer is also positioned within the outlet conduit around the stem of the valve member while a helical spring extends between the spring retainer and the valve head to urge the valve member towards its closed position. Fluid flow from the inlet conduit to the outlet conduit greater than a predetermined pressure forces the valve member open and enables fluid flow from the inlet conduit and to the outlet conduit while simultaneously creating the desired pressure drop.
These previously known back pressure inducers, however, are disadvantageous in that they impose an excessive resistance to the fluid at high fluid flow rates. Such excessive resistance creates an excessive and undesired pressure drop across the back pressure inducer at high fluid flow rates. The reasons for such excessive pressure drops at high flow rates are essentially two fold.
First, the use of a flat plate with a hole formed through it as the valve seat in combination with the conical head of the valve member produces deceleration, swirling and reacceleration of fluid flow passing through the fluid port and around the valve member head. Such turbulence in the fluid flow increases proportionately with the rate of fluid flow thus proportionally increasing the pressure drop across the back pressure inducer.
Secondly, the helical spring positioned around the stem of the valve member restricts the fluid passageway of the fluid after the fluid has passed around the head of the valve member. The fluid restriction caused by the helical spring and its retaining structure in this position further increases the pressure drop across the back pressure inducer proportionally with the fluid flow rate.